Tetrahymena pyriformis will be incubated with C14-labeled substrates - acetate, pyruvate, hexanoate, glutamate, bicarbonate - with all substrates present but only one substrate labeled in any given flask. Measurements will be made of label incorporated into CO2, lipids, glycogen, alanine, and in flasks in which glutamate is not labeled, into glutamate as well. In addition, the oxygen consumption of the cultures will be measured, and the distribution of label between the fatty acid and glycerol moieties of the lipids. Suitable structural models of intermediate metabolism, with three pools of acetyl CoA, will be drawn up, and algebraic equations will be derived predicting the steady state flux of label in each carbon atom of each substrate of the tricarboxylic acid and glyoxylate cycles and of the pathways to lipids, glycogen, glutamate, and alanine. An attempt will be made to find a set of flux rates which will yield theoretically computed values that agree with the experimentally observed ones, and thus to quantitate carbon flux along the pathways of intermediary metabolism.